[Diagnosis of microcrystalline arthropathy]

Both gout and calcium pyrophosphate dihydrate (CPPD) arthropathies are crystal deposit diseases; finding monosodium urate (MSU) or CPPD crystals in a synovial fluid sample, or in a tophi in the case of gout, provide a definitive, unequivocal diagnosis. Despite having such a simple and precise diagnostic test, in both crystal arthitides there is the accepted habit of approaching their diagnosis on clinical grounds (accompanied by hyperuricemia for gout, or chondrocalcinosis for the CPPD related arthropathy). Typical clinical presentations suggesting crystal arthitides may be due to other causes, and more important, less typical presentations, which are not uncommon, will pass undiagnosed unless crystals are systematically searched for in a synovial fluid sample from all undiagnosed arthropathies. Finally the precision of a clinical diagnosis made by an expert rheumatologist is higher than that of a less experienced or less specialized physician, and by approaching the diagnosis of the crystal arthritides on clinical grounds, expert rheumatologists support the inaccurate approach of other physicians with a wider margin of error.